In one type of known rotary piston engine, the sparking plugs are arranged in a stationary housing or in stationary side plates of the housing. The plugs are connected to the ignition current source by a high-tension lead with or without a special distributor.
In a second type of known rotary piston internal combustion engine, in which the rotor is fixedly secured to the shaft, the sparking plugs are built into the rotor, and the high tension lead for supplying current to the plugs enters the shaft from the rotor and is in the form of a distributor at the end of the shaft. The advantage of this arrangement is that the plugs can be arranged in that zone of the combustion chamber, recessed out of the rotor, which is the most favorable from the point of view of combustion. Another advantage is that each of the rotor combustion chambers can be provided with its own sparking plug around which fresh gas circulates and which is subjected to less stressing by virtue of the smaller number of sparkovers or firings of each spark plug.
In a rotary piston engine, where the rotor is not fixedly connected to the shaft but is rotatably mounted on the crank shaft or eccentric shaft supporting it, the ignition voltage cannot be supplied in the same way as in a rotary piston engine in which the rotor is fixedly secured to the shaft.
The sparking plugs in conventional rotary piston engines which are usually arranged in the trochoidal casing, are not particularly suitably positioned from the point of view of combustion. Their position is made even more unsuitable by the necessary staggering of the firing time, especially under partial load, and by the changing layer structure of the mixture.
Since the seals sweep over the housing, the plugs must not project into the working zone, but must be slightly recessed therefrom. This gives rise to the formation of a firing duct acting somewhat like a precombustion chamber which subjects the constituent material of the housing to local thermal overstressing, so that cracks can be formed in the housing.
Because of the seals which sweep over it, the outlet opening of the firing duct has to be as small as possible in order to avoid losses through overblowing. However, this is not favorable to effective ignition of all the plugs, and can result in irregular firing, especially under partial load. Another disadvantage of this conventional positioning of the plugs in the housing is that the particular plug has to fire with each revolution and is subjected to severe stressing both by the high spark frequency and by the heat generated.
An object of the present invention is to provide a system in which the sparking plugs are accommodated in the so-called combustion recesses of the piston rotors in order to obviate the disadvantages referred to above and to enable the advantages of accommodating the plugs in the rotor, both from the point of view of combustion and from the point of view of heat effect, to be obtained in rotary piston engines and in addition to link whatever may be the most favorable shape of the combustion recess, be it spherical, cylindrical or like a precombustion chamber, for example, with the ideal associated spark plug arrangement.